Beneficiaries having children will be targeted from today by new work obligations and - for them and their daughters - contraception grants.

But the Auckland Single Parents' Trust is concerned about the realities for women who are single-handedly raising a family, saying balancing work and small children is difficult even when there are two parents.

"We're going to find a lot of people breaking down. We're just going to be prepared for a bit of chaos," said the trust's organiser, Julie Whitehouse.

"We really do want society to adjust for mothers to get to work - [most] women don't want to be on the benefit - but there's got to be some common sense here."

The policy will introduce obligations of part-time work for single parents whose children are all older than 4, and full-time work for those with children older than 13.

Having more children while on the benefit will be treated as parental leave, allowing reprieve from the work obligations for a year.

Ms Whitehouse said there were genuine single mothers with three children, and juggling work and childcare, dealing with illnesses and fulfilling all the other duties of parenthood would be no easy task.

"They come home to themselves. There's no one else to support them day in, day out. It's extremely stressful," she said.

The Government will also extend grants for long-acting, reversible contraception to almost all women on benefits and the daughters of beneficiaries.